When a vehicle provided with an airbag device is involved in a collision, an airbag is inflated to restrain a vehicle occupant.
Japanese Unexamined Patent Application Publication No. 9-30367 discloses an airbag device which is capable of controlling the inflation of an airbag when a vehicle occupant or a child seat, for example, is positioned adjacent to the airbag device. According to such an airbag device, two inflators are provided for inflating the airbag. The first inflator is activated to inflate the airbag, and a pressure sensor detects the gas pressure in the airbag. If the gas pressure changes gradually in a predetermined manner, the second inflator is subsequently activated. In contrast, if the gradual change in the gas pressure is higher than usual, the second inflator is prevented from operating.
According to the airbag device in Japanese Unexamined Patent Application Publication No. 9-30367, the gradual change of the gas pressure in the airbag being inflated is determined by monitoring, but it is extremely difficult to perform such determination without allowing errors.